Search

Infections of humans with intraerythrocytic parasites of the genus Babesia can be locally prevalent in diverse regions of the United States. Transfusion of blood and blood products collected from donors infected with Babesia may result in a serious illness that can be fatal. In September 2008, the Food and Drug Administration organized a public workshop to discuss the various aspects of transfusion-transmitted babesiosis in the United States including the possible strategies to identify and defer blood donors who may have been infected with Babesia. Discussions were also held on the biology, pathogenesis, and epidemiology of Babesia species. In this article, we summarize the scientific presentations and panel discussions that took place during the workshop.

The sequence-specific suppression of HIV-1 replication using CD4 monoclonal-antibody-targeted liposomes, containing Rev antisense phosphorothioate oligonucleotides is described. Liposomes were prepared by encapsulating the 20-mer antisense DNA sequence of the rev HIV-1 regulatory gene, in the form of a phosphorothioate oligonucleotide. Specific targeting was accomplished by conjugating anti-CD4 mouse monoclonal antibody to the surface of the liposomes. HIV-1-infected H9 cells as well as peripheral blood T-lymphocytes were incubated with the immunoliposomes of antisense found to have potential antiviral effect. HIV-1 replication was reduced by 85% in antisense immunoliposome-treated H9 cells and peripheral blood lymphocytes, whereas the inhibition of HIV-1 replication was not observed using either empty immunoliposomes or immunoliposomes containing scrambled Rev phosphorothioate oligonucleotide sequences. The antiviral activity of both the free and the encapsulated oligonucleotides were assessed by p24, reverse transcriptase (RT) assays and polymerase chain reaction (PCR) analysis. Liposome preparations demonstrated minimal toxicity in H9 as well as in peripheral blood lymphocyte cell culture experiments. These in vitro culture results demonstrate the potential efficacy of immunoliposomes to inhibit HIV replication.

Polyacrylamide and starch gel electrophoresis of the hemoglobin of the killifish Fundulus heteroclitus reveal the presence of four clearly distinguishable components. These isohemoglobins, each tetramers consisting of alpha and beta chains, can be preparatively separated by ion exchange chromatography on DEAE-cellulose and are homogeneous according to isoelectric focusing in polyacrylamide gels. Oxygen equilibria of the isolated hemoglobin components (Hb I, Hb II, Hb III, and Hb IV) show only minor differences in the magnitude of the Bohr effect and in the effect of ATP on the binding of oxygen. Four different globin chains, alphaa, alphab, betaa, and betab, can be separated by ion exchange on CM-cellulose. Hb I is a homotetramer of alphab and betab chains, Hb IV consists of alphaa and betaa subunits, and components II and III are heterotetramers consisting of all four chains. The alpha and beta chains differ significantly in amino acid composition. A model suggesting the existence of 10 different isohemoglobins, 6 of which have stable intersubunit contacts, has been proposed to account for the qualitative and quantitative aspects of the electrophoretic behavior of the components. Separations of the isohemoglobins on DEAE-cellulose under slightly modified conditions provide additional support for the model.

Glycogen synthase (UDP glucose: glycogen alpha-4-glycosyltransferase, EC2.4.1.11) of the tapeworm Hymenolepis diminuta exists in 2 forms: 1) the I-form (independent), which has significant activity in the absence of glucose 6-phosphate (G6P); and 2) the phosphorylated D-form (dependent), which has no enzymatic activity unless G6P is present. The activity of the I-form is greatly enhanced by a variety of allosteric effectors which have, as their common feature, 1 or more phosphate groups. These include inorganic phosphate (Pi), several sugar phosphates, some phosphorylated glycolytic intermediates, and nucleoside mono- and triphosphates. Competition studies suggest that while most of the positive effectors act at the same site on the enzyme (the "G6P site"), fructose 1,6-diphosphate (FDP) and 2,3-diphosphoglyceric acid (2,3DPG) act at low concentrations to stimulate the enzyme at another locus (the "diphosphate site"), while at high concentrations they competitively inhibit the binding of G6P and of the other activators. The inhibition by high uridine monophosphate (UMP) concentrations is competitive only with the activator uridine triphosphate (UTP), suggesting the existence of a third type of allosteric site (the "uridine nucleotide site"). This third site may be the locus for feedback inhibition by the product uridine diphosphate (UDP), a control mechanism which has been observed to occur in mammalian systems. The allosteric control of the D-form of the enzyme is comparatively simple, apparently involving only one site (the "G6P site") that binds a few effects with greatly reduced affinity. Pi reverses the activation of the D-form by G6P.

Glycogen synthase I (UDP glucose: glycogen alpha-4-glycosyltransferase, EC2.4.1.11) of the tapeworm Hymenolepis diminuta is the form of the enzyme which is active in vivo, while the D-form represents an inactive "storage form." Utilizing the differential effect of inorganic phosphate (Pi) on the I and D-forms, the ratio of the 2 forms in vivo has been determined under conditions of starvation of the host and refeeding of the parasite with glucose. This procedure reveals that conversion of the inactive D-form to the active I-form takes place when glycogen-depleted worms are incubated in glucose. The activity of glycogen synthase I also is affected by the molecular weight of the primer glycogen. With certain molecular weight fractions, enzymatic activity is higher than with others. This specificity of the glycogen primer could explain the relatively low concentrations of those molecular weight fractions which confer the highest synthase activity.